Phat does mean Pretty Hot And Tempting, like the other definitions say. The problem with "phat" is that it is no longer in really. It has kind of phased out and is mostly used by wannabes, lowerclassmen in high school, or middle schoolers. It is now considered a slang faux pas. I wouldn't use it if I was you.

14 year old: "That's phat man."
22 year old: "Um, dude, that word got old in the late '90s"

Pathetic Kid: God, that chick is PHAT, man...
Dumb Kid: What? I don't think she's fat.
Pathetic Kid: No, dude. Phat as in Pretty Hot and Tempting.
Dumb Kid: Cool! I think I'll be pathetic like you and use it!
Me: *kills them for being pathetic*

In the 80s, an 18 year old inner-city black kid from Richmond, Virginia told me that it stood for "Pussy, Hips, Ass, Tits", And he told me this around 1985. So that word is AT LEAST 27 years old. True Story. Just thought I'd share with you.

1. A word to describe a rhythm that one likes. Comes from back in the old days, when people would call certain beats in songs "fat," referring to their presance. It's been adopted into slang rather recently, probably in the late 80s.

2. Often made into the backronym of "pretty hot and tempting." This is not what it originally stood for, but things change.